I purchased my ST with almost 3K miles on it from a local dealer who Gold Certified it. I have always thought the engine was loud at startup and just accepted it as normal. This is the first time owning a turbo'd engine and I am still learning the nuances between forced induction and NA engines noises. I chalked the noise up to direct injection and the turbos... But I am not certain any more. I think there are 2 different sounds going on here. The first appears to be a startup rattle that I believe is from the engine and lasts maybe a second on cold start. The second is another rattle but sounds like it is coming from underneath, lasts several seconds while the truck warms up. My first thought is a flex pipe. Both noises are gone within 30 seconds of a cold start and do not happen again once warm. I tried to capture the sounds in this video. I am open for some comments from the group before I make a decision to make an appointment at the dealer.
https://drive.google.com/file/d/14JqL-Uwzn_IDosMGSVXxvyOq4IrdO9CN/view?usp=drive_link
https://drive.google.com/file/d/14JqL-Uwzn_IDosMGSVXxvyOq4IrdO9CN/view?usp=drive_link